Leaves on the plant of Bryophyllum calycinum produce foliar embryos in the notches of the leaf margin. These embryos remain dormant while the leaf is attached to the plant. However, detaching a leaf will cause many of these foliar embryos to be released from dormancy and develop into plantlets. The effects of thidiazuron (TDZ), a hormone with cytokinin activity, on the release of foliar embryos and root formation was investigated. Two centimeter explants of the leaf margin including the notch region were removed from the leaves and grown in tissue culture on Murashige and Skoog media supplement with B5 vitamins and various hormones. Overall, TDZ causes significantly more embryos to be released from dormancy compared to the control or some concentrations of 6-Benzly-aminopurine (BAP). At concentrations of 10-8 and 10-10 TDZ, greater than 92% of the foliar embryos placed in culture were released from dormancy compared to 84% or 82% on 10-6 or 10-8 BAP, respectively, or 73% on the control media. In addition, a trend was observed that higher concentrations of TDZ causes the release of fewer embryos than lower concentrations. TDZ at various concentrations had little affect on the number of roots per explant unlike BAP or 2,4-D compared to the control.

Key words: asexual reproduction, Bryophyllum calycinum, Crassulaceae, foliar embryo, thidiazuron